Process of producing material for use in the casting of photographic film support



United States Patent PROCESS OF PRODUCING MATERIAL FOR USE IN THE CASTING OF PHOTOGRAPHIC FILM SUP- PORT Gustaaf Adam, Antwerp-Wilrijk, and Remi Gustave Tritsmans, Antwerp-Mortsel, Belgium, assignors to Gevaert Photo-Producteu N. V., Antwerp-Mortsel, Belgium, a Belgian company No Drawing. Application July 11, 1952, Serial No. 298,468. In Germany September 9, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires September 9, 1962 9 Claims. (Cl. 117-118) This application is a continuation-in-part of our copending application Serial No. 5,174, filed January 29. 1948, now abandoned, and the latter application is a division of our application Serial No. 734,830, filed March 14, 1947, now abandoned.

This invention relates to a process for the manufacture of photographic film support.

It is an object of this invention to produce cellulose lower fatty acid ester layers, which have been saponified to a depth especially suitable for the casting of films or sheets; for instance, photographic film supports.

More particularly it is an object of this invention to provide the drum or belt of a casting machine with a layer, the so-called casting layer, which consists of a cellulose lower fatty acid ester having an outer portion down to a substantial depth of de-esterified cellulose.

In the manufacture of cellulose ester sheets for photographic film supports, it is known to pour the solution of a film-forming compound on a support, called the carrier, which may be either a metal surface having a very high gloss, such as a nickel or silver surface or may be the surface of an endless metal band (belt) covered with a layer of a high-polymeric surface, called the casting layer.

Hitherto, this casting layer consisted of gelatin or of a cellulose ester. However, since these materials do not possess the necessary properties to form sheets having a very high gloss, and since sheets cast on cellulose ester often stick to the casting layer, it has been proposed to superficially change the substance of the cellulose ester forming the casting layer by treating its surface with a de'esterifying liquid, for instance an aqueous solution of potassium-hydroxide.

However, in the practice of this method great drawbacks are encountered. It is very difficult, if not impossible to preserve the high gloss of the casting layer by applying the saponifying liquid directly on this layer. Furthermore, due to salt formation, the penetration of the alkali into the casting layer is limited to a depth of about 10a. For instance if cellulose acetate is saponified with potassium hydroxide, potassium acetate is formed which cannot be removed completely in the known processes and hinders penetration of the alkali to a sufficient depth.

In many cases, for instance when preparing casting layers for the manufacture of photographic film support of cellulose derivatives, this penetration to 10p is altogether insufiicient. If, when casting film support, the solvent of the film-forming product also is a solvent for the unsaponified cellulose ester of the casting layer, this solvent might difiuse, by the capillary action of impurities present in the casting layer, into unsaponified cellulose ester in the inner part of the casting layer and might cause the cast film support to adhere to thecasting layer.

According to the present invention, these disadvan- 2,716,077 ?atented Aug. 23, 1955 ice tages can be avoided, if the surface of the casting layer, composed of a cellulose ester, and preferably of a lowerfatty acid ester, is coated with a hydrophilic colloid, preferably gelatin, and the saponifying liquid, preferably an aqueous alkali metal hydroxide, is spread on this hydrophilic colloid layer. The liquid then penetrates by diffusion into the cellulose ester layer, saponifying it to a certain depth. After the saponifying process has thus been carried through to the desired depth, the colloid layer is removed.

We have now found that so-obtained saponified cellulose ester layers are completely satisfactory as a casting layer in the manufacture of films or sheets.

Since the saponifying liquid is not spread directly on the surface of the layer to be saponified, this surface is not damaged and its high gloss remains intact. Consequently the film formed on it possesses a very high gloss.

Further, in performing the saponification in the above described manner, no screening salt layer is formed on the surface of the casting layer, because the salts that may be formed, immediately diifuse into the water-containing layer. The saponifying process may thus be guided at will to any desired depth and even through the entire thickness of the cellulose ester layer, by either applying the saponifying liquid or by applying it repeatedly.

In this manner, the adhesion of the cast film on the cellulose casting layer may be avoided, and the films are stripped oif without damaging the high gloss. If the casting layer is a composite layer formed of several layers made of the same or of different cellulose esters, it is convenient to saponify completely through the top layer 0;? layers into the region of an underlying layer, for instance where the cellulose lower fatty acid ester coating is composed of three layers each having a thickness of 0.06 mm. (total thickness 0.18 mm.) a depth of saponification of 0.15 mm. may be reached.

In practicing the process of the present invention the belt of a casting machine is provided with a lower fatty acid ester layer. This coating may be produced by dissolving a suitable ester as for example, a cellulose acetate, propionate, butyrate and/ or mixtures thereof such as aceto-butyrates in a suitable organic solvent therefore and applying the solution in a known manner to the metal belt. After the casting layer has dried it is covered with a solution of gelatin in warm water. Preferably the gelatin solution also contains an agent capable of stabilizing against alkali, the gelatin layer to be formed. This stabilizing agent is preferably a sugar or sugar-like substance of the type already known as modifying agent for gelatin. Preferably the sugar or sugarlike substance is a hexitol such as sorbitol, or a hexose or pentose such as glucose, fructose and arabinose or a mixture of monosaccharide such as invert sugar which contains both glu cose and fructose, or a disaccharide such as sucrose.

When speaking of gelatin in relation with the present invention, we mean gelatin as such or in the presence of a stabilizing agent of the type already known and as indicated above.

In any event the gelatin solution is cooled to approximately room temperature whereupon it solidifies or jellifies. 'The gelatin surface is then treated with an aqueous solution of an alkali metal hydroxide as for example, sodium lithium or potassium hydroxide. 'Preferably a solution having a concentration of from 3 to 30% by weight of alkali metal hydroxide is used; The gelatin layer may be treated any number of times with thealkali depending on the penetration desired. Thereafter the gelatin layer is stripped from the ester layer and a perfectly smooth surface having a substantial depth of deesterification or saponification is disclosed. I

The following specific examples serve to illustrate bu are not intended to limit the present invention.

solution also contained 1 kgm. of sorbitol.

Example I A solution of 13 kgms. cellulose acetate in 100 litres acetone is coated in three superimposed layers on the endless belt of a band-casting machine. After drying, the castinglayer thus produced is covered with a solution of 15 kgms. gelatin in 30 litres water at 55 C. The On cooling to C. the gelatin jellifies. This gelatin is treated ten times running with a 20% aqueous potassium hydroxide solutionand is then removed. The casting layer laid bare after this removal still showsa perfect high gloss. It is inert to the usual solvents, being converted into regenerated cellulose to a depth of IOO Qand therefore is a very suitable casting layer for films support of every kind. 7

Example [I An endless travelling copper band is coated during three revolutions of the band withan 18% acetone solution of cellulose acetate containing 40% acetylJ The' After 14 complete revolutions of the band, which occurs within about 4% hours, the saponification treatment is interrupted and the gelatin layer is washed in order to remove all residual alkali and salts, by gently dabbing it with props of cotton wool impregnated with cooled water. After 3 hours washing, the gelatin layer is dried in a moderately warm air current. After a rest period of 2% minutes, said .layer is removed and the cellulose acetate layer is dried in a warm air current. The saponification depth is found to be about 0.10 mm. 7

t 7 Example 111 15 parts by weight of a partially hydrolysed cellulose aceto propionate with a 5% propionyl content and a 35% acetyl' content' are dissolved in 100 litres acetone and coated withintwo revolutions onto the endless copper band of a casting machine, forming in this Way a 0.16 mm. thick composite layer. After'drying and polishing the overlap, a hot solution of 50 parts by weight of gelatin in, 100 parts of water, stabilized by invert sugar added in an amount of 3rparts by Weight is coated onto the cellulose ester layer in a thickness of about 5 mm. A NaOH solution in 100 parts by volume of an equal mixture of methanol and water is applied to and removed from this gelatin layer as described in Example I. The dried cellulose ester is saponified to a depth of about 0.12 mm.

Example IV 14 parts by weight of partially hydrolysed cellulose aceto butyrate with a 10% butyryl content and a 32% acetyl content are dissolved in 100 litres acetone. This After 7 this layer is further superficially hydrolysed through a gelatin layer as describedin Example I. The gelatin layer contains as stabilizer 5% fructose on the Weight of the gelatin and has a thickness of 5 mm. while the.

saponifying liquid contains NaOH in parts of water and parts by volume of methanol. A depth 1 of saponification of 0.15 mm. is reached.

Example V1 fication is completed in 10 hours and reaches a depth of 0.11 mm.

The casting layers, obtainedaccording to the above examples possess a perfect high'gloss and are excellently suited to the casting of photographic film supports.

We claim:

1. The process of producing a casting layer for the manufacture of photographic film support, which comprises coatmgthe surface of a sheet of cellulose lower fatty acid ester soluble in an organic solvent with an aqueous solution of gelatin, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing from 3 to 30 percent by weight of alkali metal hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, saponifying said cellulose lower fatty acid ester'sheet and then rernoving the gelatin layer.

2. The process of producing a casting layer for the manufacture of photographic film support, which comprises coating the surface of a sheet of cellulose lower fatty acid ester soluble in an organic solvent with an aqueous solution of gelatin which contains at least one stabilizing agent selected from the group consisting of disaccharide, pentose, hexose and hexitol, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing from 3 to 30 percent by weight of alkali metal hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, saponifying said cellulose lower fatty acid ester sheet, and then removing the gelatin layer..

3. Theprocess of producing a casting layer for the manufacture of photographic film support, which comsolution is coated onto the endless band of the casting machine, dried and superficially hydrolysed asdescribed in Example I through the gelatin layer containing as a stabilizer 2% arabinose on the weight of the gelatine.

'The saponifying liquid contains 25% of KOH in a mix- Example V 10 parts by weightof a cellulose acetate with a 43% acetyl content are dissolved in litres methylene chloride and coated onto the endless band of the castingmachine inthree revolutions. After drying and polishing,

prises coating the surface of a sheet of cellulose lower fatty acid ester soluble in an organic solvent with an aqueous solution of gelatin, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing approximately from 3 to 10 percent by weight of lithium hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, sapouifying said cellulose lower fatty acid ester sheet, and then removing the gelatin layer.

4. The process of producing a casting layer for the manufacture of photographic film support, which cornprises coating the surface of a sheet of cellulose lowerprises coating the ,surface of a sheet of cellulose lower fatty acid ester soluble in an organic solvent with an aqueous solution of gelatin, allowing this solution to set, spreading on the thus obtainedgelatin layer an aqueous solution containing approximately from 5 to 30 percent by weight of potassium hydroxide, allowing the aqueous solution to diffuse through the gelation layer, saponifying said cellulose lower fatty acid ester sheet, and then removing the gelatin layer.

6. The process of producing a casting layer for the manufacture of photographic film support, which com-- prises coating the surface of a sheet of cellulose acetate, soluble in an organic solvent with an aqueous solution of gelatin, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing from 3 to 30 percent by Weight of alkali metal hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, saponifying said cellulose acetate sheet, and then removing the gelatin layer.

7. The process of producing a casting layer for the manufacture of photographic film support, which comprises coating the surface of a sheet of cellulose aceto propionate soluble in an organic solvent with an aqueous solution of gelatin, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing from 3 to 30 percent by weight of alkali metal hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, saponifying said cellulose aceto propionate sheet, and then removing the gelatin layer.

8. The process of producing a casting layer for the manufacture of photographic film support, which comprises coating the surface of a sheet of cellulose aceto butyrate soluble in an organic solvent with an aqueous solution of gelatin, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing from 3 to 30 percent by weight of alkali metal hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, saponifying said celluluose aceto butyrate sheet, and then removing the gelatin layer.

9. The process of producing a casting layer for the manufacture of photographic film support, which comprises coating the surface of a sheet of cellulose acetate soluble in an organic solvent with an aqueous solution of gelatin containing sorbitol, allowing this solution to set, spreading on the thus obtained gelatin layer an aqueous solution containing from 3 to 30 percent by weight of potassium hydroxide, allowing the aqueous solution to diffuse through the gelatin layer, saponifying said cellulose acetate sheet, and then removing the gelatin layer.

References Cited in the file of this patent UNITED STATES PATENTS 1,988,550 Gladhorn Jan. 22, 1935 2,092,005 Moncrieff Sept. 7, 1937 2,116,063 Dreyfus May 3, 1938 2,558,555 Hendricx June 26, 1951 FOREIGN PATENTS 897,404 France Mar. 21, 1945 

1. THE PROCESS OF PRODUCING A CASTING LAYER FOR THE MANUFACTURE OF PHOTOGRAPHIC FILM SUPPORT, WHICH COMPRISES COATING THE SURFACE OF A SHEET OF CELLULOSE LOWER FATTY ACID ESTER SOLUBLE IN AN ORGANIC SOLVENT WITH AN AQUEOUS SOLUTION OF GELATIN, ALLOWING THIS SOLUTION TO SET, SPREADING ON THE THUS OBTAINED GELATIN LAYER AN AQUEOUS SOLUTION CONTAINING FROM 3 TO 30 PERCENT BY WEIGHT OF ALKALI METAL HYDROXIDE, ALLOWING THE AQUEOUS SOLUTION TO DIFFUSE THROUGH THE GELATIN LAYER, SAPONIFYING SAID CELLULOSE LOWER FATTY ACID ESTER SHEET AND THAN REMOVING THE GELATIN LAYER. 